Goodwill and Other Intangible Assets - Goodwill (Details) $ in Millions	3 Months Ended
	Mar. 31, 2016 USD ($)
Goodwill [Roll Forward]
Goodwill, beginning of period	$ 71.1
Goodwill adjustments	(0.6)
Goodwill, end of period	70.5
Domestic Coke
Goodwill [Roll Forward]
Goodwill, beginning of period	3.4
Goodwill adjustments	0.0
Goodwill, end of period	3.4
Coal Logistics
Goodwill [Roll Forward]
Goodwill, beginning of period	67.7
Goodwill adjustments	(0.6)
Goodwill, end of period	$ 67.1